1. Field of the Invention
This invention relates generally to electronic devices and environment-dependent methods of maintaining the devices and indicating operational status of the devices. In particular, this invention relates to temperature-dependent methods of maintaining external defibrillators and indicating their operational status.
2. Description of the Prior Art
Electronic devices that are infrequently used may be designed to perform automatic self-tests on a preset schedule, in response to an event or condition, or otherwise and to indicate the results of those self-tests to a potential user. An example can be found in certain external defibrillators that automatically self-test battery capacity and other defibrillator functions and components and indicate the results of those self-tests (ie., the device's operational status) through visual displays and/or audible tones.
U.S. patent application Ser. No. 08/240,272 describes a battery-operated automatic external defibrillator (AED) designed for infrequent use. The device described in that patent application performs a variety of daily, weekly and monthly self-tests while in stand-by mode (i.e., when not powered-on to treat a patient, to review past treatment events, etc.) and indicates the operational status of the device using an "OK" or "Not OK" fail-safe display and through an audible tone generator. One of the device parameters monitored during the self-tests is remaining battery capacity.
The '272 application also suggests performing a group of self-tests automatically in response to exposure of the defibrillator to temperature extremes, although the exact nature of the environmentally-triggered self-tests is not disclosed.
The disclosure of the '272 application is incorporated herein by reference.